Urgent Motor Help Needed After Tuneup

[PlayingWithTBI]

Those normally just die altogether.

Not always, I've had a bad ICM and coil but it still ran OK. Just rough at idle and RPM spikes when cruising around 2000 RPM. Changed the IAC and cured the spikes but, it still idled rough until I changed the coil. I sprayed some water on the electrical components until the engine almost died when I hit the coil.
Burnt coil (after 2000 miles), look at the marks on the coil and iron.

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Here's when I was going ~60 MPH/2000 RPM. The timing would jump every so often. It took a while data logging until the slow-ass 7747 ECM showed up on TunerPro RT.

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[PlayingWithTBI]

Replaced coil with AC Delco and tossed in DynaMod ICM

Is that coil a GM Original or one of their lower level stuff? I'm using the GM Original pn19418995 - no issues since.

The Spectronic IAC only lasted a couple thousand miles (and an Accel coil lasted less than that) until I put in an AC Delco 1984A (GM Original too)

Accel coil - same kind of arcing...

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[Nick88]

Is that coil a GM Original or one of their lower level stuff? I'm using the GM Original pn19418995 - no issues since.

The Spectronic IAC only lasted a couple thousand miles (and an Accel coil lasted less than that) until I put in an AC Delco 1984A (GM Original too)

Accel coil - same kind of arcing...

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Not sure about the coil, looked and felt high-quality was around $100. I used to run Accel coil and it has a spot exactly like yours I thoughtnit was burnt. Ended up being a little dot of carbon from when I cleaned EGR passage with EGR off.

DynaMod ICMs seem ok knock on wood, I really like when its running good the idle feels much smoother than the AcDelco ones. Ive actually had a few ACDelco ICMs that were bad out of the box

 

[PlayingWithTBI]

Not sure about the coil, looked and felt high-quality was around $100. I used to run Accel coil and it has a spot exactly like yours I thoughtnit was burnt.

Did you try spraying water on the electrical components while idling to see if it stumbles? Including the 4-wire ICM connector on the back of the distributor.

 

[Nick88]

Did you try spraying water on the electrical components while idling to see if it stumbles? Including the 4-wire ICM connector on the back of the distributor.

Ill give it a try, all wiring connectors are replaced after I had an issue eith the 4 wire connector pigtail. What are the common reasons that would cause the idle to be surging

 

[PlayingWithTBI]

What are the common reasons that would cause the idle to be surging

A scanner would help with that. Did you eliminate all of your DTCs?

 

[Nick88]

Did you try spraying water on the electrical components while idling to see if it stumbles? Including the 4-wire ICM connector on the back of the distributor.

Also I forgot to mention when I have the timing wire unplugged and am setting base timing the idle surges a little bit, it did this before It started happening at normal idle.

 

[PlayingWithTBI]

Also I forgot to mention when I have the timing wire unplugged and am setting base timing the idle surges a little bit, it did this before It started happening at normal idle.

How about checking for slop in the distributor shaft and gear. Pop the cap off and turn the rotor back and forth to see if there is any slop. While in there look at your pickup coil to see if it's broken/cracked.

Timing chain probably not an issue but check it too. While looking at the rotor, rotate the crank back and forth to see if there's any slop there.

 

[Nick88]

How about checking for slop in the distributor shaft and gear. Pop the cap off and turn the rotor back and forth to see if there is any slop. While in there look at your pickup coil to see if it's broken/cracked.

Timing chain probably not an issue but check it too. While looking at the rotor, rotate the crank back and forth to see if there's any slop there.

No slop Ive checked that since Ive had cheap distributors before that turn a ton. No cracks I can see either. How would I check the timing chain for slack? Motor has around 120K on the clock

 

[Orpedcrow]

What are the common reasons that would cause the idle to be surging

Idle Air Control Valves and vacuum leaks. I think watching the fuel trims while it’s doing it will confirm. Ecm sees a “lean condition” and dumps a bunch of fuel, then it’s a “rich condition” and it pulls it all back out and it just cycles back and forth surging because it can’t maintain the unmetered air leak.